GoPLC Math, String & Conversion Reference

James M. Belcher Founder, JMB Technical Services LLC April 2026 | GoPLC v1.0.535

1. Math & Trigonometry

Basic Math

Function	Signature	Returns	Description
`ABS`	`(x)`	REAL/INT	Absolute value
`SIGN`	`(x)`	INT	-1, 0, or 1
`SQRT`	`(x)`	REAL	Square root
`POW`	`(base, exp)`	REAL	Power (base^exp)
`EXPT`	`(base, exp)`	REAL	Same as POW
`EXP`	`(x)`	REAL	e^x
`LN`	`(x)`	REAL	Natural logarithm
`LOG`	`(x)`	REAL	Base-10 logarithm
`FMOD`	`(x, y)`	REAL	Floating-point modulus

distance := SQRT(POW(x2 - x1, 2) + POW(y2 - y1, 2));
gain_db := 20.0 * LOG(vout / vin);

Rounding

Function	Signature	Returns	Description
`CEIL`	`(x)`	REAL	Round up to integer
`FLOOR`	`(x)`	REAL	Round down to integer
`ROUND`	`(x)`	REAL	Round to nearest integer
`TRUNC`	`(x)`	REAL	Truncate toward zero

pages := CEIL(total_items / 10.0);      (* 25 items → 3 pages *)
whole := TRUNC(3.7);                     (* 3.0 *)

Trigonometry

All angles in radians.

Function	Signature	Returns	Description
`SIN`	`(rad)`	REAL	Sine
`COS`	`(rad)`	REAL	Cosine
`TAN`	`(rad)`	REAL	Tangent
`ASIN`	`(x)`	REAL	Arc sine (returns radians)
`ACOS`	`(x)`	REAL	Arc cosine
`ATAN`	`(x)`	REAL	Arc tangent
`ATAN2`	`(y, x)`	REAL	Two-argument arc tangent
`DEG_TO_RAD`	`(deg)`	REAL	Degrees → radians
`RAD_TO_DEG`	`(rad)`	REAL	Radians → degrees

angle_rad := DEG_TO_RAD(45.0);
x := COS(angle_rad) * radius;
y := SIN(angle_rad) * radius;
heading := RAD_TO_DEG(ATAN2(dy, dx));

2. Selection & Comparison

Function	Signature	Returns	Description
`MIN`	`(a, b)`	ANY	Smaller of two values
`MAX`	`(a, b)`	ANY	Larger of two values
`LIMIT`	`(min, value, max)`	ANY	Clamp value to range
`CLAMP`	`(value, min, max)`	ANY	Same as LIMIT (different arg order)
`SEL`	`(condition, false_val, true_val)`	ANY	Conditional select (like ternary)
`MUX`	`(index, val0, val1, val2, ...)`	ANY	Indexed multiplexer

(* Clamp output to 0-100% *)
output := LIMIT(0.0, pid_output, 100.0);

(* Select based on condition *)
mode_name := SEL(auto_mode, 'MANUAL', 'AUTO');

(* Multiplexer — select by index *)
recipe_temp := MUX(recipe_id, 150.0, 180.0, 200.0, 220.0);

3. Statistics

Function	Signature	Returns	Description
`MEAN`	`(array)`	REAL	Arithmetic mean
`MEDIAN`	`(array)`	REAL	Middle value
`VARIANCE`	`(array)`	REAL	Population variance
`STDDEV`	`(array)`	REAL	Standard deviation
`PERCENTILE`	`(array, pct)`	REAL	Nth percentile (0-100)
`MOVING_AVG`	`(handle, value, window)`	REAL	Moving average (handle-based)
`SMA`	`(handle, value, window)`	REAL	Simple moving average (alias)
`EMA`	`(handle, value, alpha)`	REAL	Exponential moving average

temps := ARRAY_CREATE(68.2, 72.1, 71.5, 73.0, 69.8);
avg := MEAN(temps);                    (* 70.92 *)
med := MEDIAN(temps);                  (* 71.5 *)
sd := STDDEV(temps);                   (* ~1.8 *)
p95 := PERCENTILE(temps, 95);         (* ~72.8 *)

(* Running average over last 20 samples *)
smooth_temp := MOVING_AVG('temp_avg', raw_temp, 20);

(* Exponential smoothing — alpha 0.1 = heavy smoothing *)
filtered := EMA('pressure_ema', raw_pressure, 0.1);

4. Interpolation & Scaling

Function	Signature	Returns	Description
`LERP`	`(a, b, t)`	REAL	Linear interpolation (t=0→a, t=1→b)
`SCALE`	`(value, in_min, in_max, out_min, out_max)`	REAL	Map range to range
`RANDOM`	`()`	REAL	Random 0.0–1.0
`RAND`	`()`	REAL	Alias for RANDOM
`RANDOM_RANGE`	`(min, max)`	REAL	Random in range

(* Scale 0-4095 ADC to 0-100 PSI *)
pressure_psi := SCALE(adc_raw, 0, 4095, 0.0, 100.0);

(* Fade between two colors over 100 steps *)
brightness := LERP(0.0, 100.0, INT_TO_REAL(step) / 100.0);

(* Simulate sensor noise *)
noisy := actual_temp + (RANDOM_RANGE(-0.5, 0.5));

5. Unit Conversions

Function	Signature	Returns	Description
`C_TO_F`	`(celsius)`	REAL	Celsius → Fahrenheit
`F_TO_C`	`(fahrenheit)`	REAL	Fahrenheit → Celsius
`C_TO_K`	`(celsius)`	REAL	Celsius → Kelvin
`K_TO_C`	`(kelvin)`	REAL	Kelvin → Celsius
`KMH_TO_MS`	`(kmh)`	REAL	km/h → m/s
`MS_TO_KMH`	`(ms)`	REAL	m/s → km/h
`DEG_TO_RAD`	`(degrees)`	REAL	Degrees → radians
`RAD_TO_DEG`	`(radians)`	REAL	Radians → degrees

6. String Functions

Length & Access

Function	Signature	Returns	Description
`LEN`	`(str)`	INT	String length
`LEFT`	`(str, count)`	STRING	First N characters
`RIGHT`	`(str, count)`	STRING	Last N characters
`MID`	`(str, start, count)`	STRING	Substring (1-based start)
`CHR`	`(code)`	STRING	ASCII code → character
`ORD`	`(str)`	INT	First character → ASCII code

name := 'GOPLC-Plant1';
prefix := LEFT(name, 5);              (* "GOPLC" *)
suffix := RIGHT(name, 6);             (* "Plant1" *)
mid := MID(name, 7, 6);               (* "Plant1" *)
newline := CHR(10);                    (* \n *)

Search

Function	Signature	Returns	Description
`FIND`	`(str, search)`	INT	Position of substring (0 = not found)
`CONTAINS`	`(str, search)`	BOOL	Substring exists?
`STARTS_WITH`	`(str, prefix)`	BOOL	Starts with prefix?
`ENDS_WITH`	`(str, suffix)`	BOOL	Ends with suffix?

IF CONTAINS(alarm_text, 'HIGH') THEN
    severity := 3;
END_IF;

Modify

Function	Signature	Returns	Description
`CONCAT`	`(str1, str2, ...)`	STRING	Join strings (variadic)
`REPLACE`	`(str, search, replacement)`	STRING	Replace all occurrences
`INSERT`	`(str, position, insert_str)`	STRING	Insert at position
`DELETE`	`(str, position, count)`	STRING	Delete characters
`UPPER`	`(str)`	STRING	Uppercase
`LOWER`	`(str)`	STRING	Lowercase
`TRIM`	`(str)`	STRING	Strip whitespace both ends
`LTRIM`	`(str)`	STRING	Strip leading whitespace
`RTRIM`	`(str)`	STRING	Strip trailing whitespace
`REVERSE`	`(str)`	STRING	Reverse string
`REPEAT`	`(str, count)`	STRING	Repeat N times
`PAD_LEFT`	`(str, width, pad_char)`	STRING	Left-pad to width
`PAD_RIGHT`	`(str, width, pad_char)`	STRING	Right-pad to width
`SPLIT`	`(str, delimiter)`	ARRAY	Split into array
`FORMAT`	`(template, args...)`	STRING	Printf-style formatting

msg := CONCAT('Temperature: ', REAL_TO_STRING(temp), ' F');
csv := REPLACE(raw_data, ';', ',');
parts := SPLIT('10.0.0.50:502', ':');       (* ["10.0.0.50", "502"] *)
padded := PAD_LEFT(INT_TO_STRING(batch), 6, '0');  (* "000042" *)
line := FORMAT('%s,%d,%.2f', tag_name, count, value);

7. Type Conversions

Numeric

From \ To	INT	DINT	REAL	STRING	BOOL	BYTE	WORD	DWORD
INT	—	`INT_TO_DINT`	`INT_TO_REAL`	`INT_TO_STRING`	`INT_TO_BOOL`	`INT_TO_BYTE`	`INT_TO_WORD`	`INT_TO_DWORD`
DINT	`DINT_TO_INT`	—	`DINT_TO_REAL`	`DINT_TO_STRING`	—	`DINT_TO_BYTE`	`DINT_TO_WORD`	—
REAL	`REAL_TO_INT`	`REAL_TO_DINT`	—	`REAL_TO_STRING`	—	`REAL_TO_BYTE`	`REAL_TO_WORD`	`REAL_TO_DWORD`
STRING	`STRING_TO_INT`	`STRING_TO_DINT`	`STRING_TO_REAL`	—	`STRING_TO_BOOL`	`STRING_TO_BYTE`	`STRING_TO_WORD`	`STRING_TO_DWORD`
BOOL	`BOOL_TO_INT`	`BOOL_TO_DINT`	—	`BOOL_TO_STRING`	—	`BOOL_TO_BYTE`	`BOOL_TO_WORD`	`BOOL_TO_DWORD`
BYTE	`BYTE_TO_INT`	—	`BYTE_TO_REAL`	`BYTE_TO_STRING`	—	—	`BYTE_TO_WORD`	`BYTE_TO_DWORD`
WORD	`WORD_TO_INT`	—	`WORD_TO_REAL`	`WORD_TO_STRING`	—	`WORD_TO_BYTE`	—	`WORD_TO_DWORD`
DWORD	`DWORD_TO_INT`	`DWORD_TO_DINT`	`DWORD_TO_REAL`	`DWORD_TO_STRING`	—	`DWORD_TO_BYTE`	`DWORD_TO_WORD`	—

Extended Integer Types

Function	Description
`UINT_TO_INT`, `INT_TO_UINT`	Unsigned ↔ signed 16-bit
`UDINT_TO_DINT`, `DINT_TO_UDINT`	Unsigned ↔ signed 32-bit
`LINT_TO_INT`, `INT_TO_LINT`	64-bit ↔ 32-bit
`ULINT_TO_UINT`, `UINT_TO_ULINT`	Unsigned 64-bit ↔ 16-bit
`SINT_TO_STRING`, `USINT_TO_STRING`	Short int → string

Date & Time

Function	Description
`TIME_TO_STRING`, `STRING_TO_TIME`	TIME ↔ STRING
`TIME_TO_DINT`, `DINT_TO_TIME`	TIME ↔ milliseconds
`TIME_TO_REAL`, `REAL_TO_TIME`	TIME ↔ seconds (float)
`DATE_TO_STRING`, `STRING_TO_DATE`	DATE ↔ STRING
`DT_TO_STRING`, `STRING_TO_DT`	DATE_TIME ↔ STRING
`DT_TO_DATE`, `DATE_TO_DT`	Extract/build date portion
`DT_TO_TOD`, `TOD_TO_TIME`	Extract/build time-of-day
`DATE_TO_DWORD`, `DWORD_TO_DATE`	DATE ↔ binary
`DT_TO_DWORD`, `DWORD_TO_DT`	DATE_TIME ↔ binary
`TOD_TO_DINT`, `DINT_TO_TOD`	Time-of-day ↔ integer

Number Base

Function	Description
`INT_TO_HEX`, `HEX_TO_INT`	Integer ↔ hex string
`DINT_TO_HEX`, `HEX_TO_DINT`	32-bit ↔ hex string
`INT_TO_BIN`, `BIN_TO_INT`	Integer ↔ binary string
`DINT_TO_BIN`, `BIN_TO_DINT`	32-bit ↔ binary string
`INT_TO_OCT`, `OCT_TO_INT`	Integer ↔ octal string
`DINT_TO_OCT`, `OCT_TO_DINT`	32-bit ↔ octal string
`BYTE_TO_GRAY`, `GRAY_TO_BYTE`	Binary ↔ Gray code

hex := DINT_TO_HEX(255);              (* "FF" *)
val := HEX_TO_INT('1A');               (* 26 *)
gray := BYTE_TO_GRAY(13);              (* Gray code encoding *)

8. Bitwise Operations

Operator	Syntax	Description
`AND`	`a AND b`	Bitwise AND
`OR`	`a OR b`	Bitwise OR
`XOR`	`a XOR b`	Bitwise XOR
`NOT`	`NOT a`	Bitwise NOT
`SHL`	`SHL(value, bits)`	Shift left
`SHR`	`SHR(value, bits)`	Shift right
`ROL`	`ROL(value, bits)`	Rotate left
`ROR`	`ROR(value, bits)`	Rotate right
`SET_BIT`	`SET_BIT(value, bit)`	Set bit N

(* Extract bits from a status word *)
motor_running := (status_word AND 16#0001) > 0;     (* Bit 0 *)
fault_active := (status_word AND 16#0002) > 0;       (* Bit 1 *)

(* Build a command word *)
cmd := 0;
IF start THEN cmd := cmd OR 16#0001; END_IF;
IF forward THEN cmd := cmd OR 16#0004; END_IF;

9. Complete Example: Sensor Signal Processing

PROGRAM POU_SignalProcessing
VAR
    (* Raw inputs *)
    adc_raw : INT;                     (* 0-4095 from ADC *)
    pressure_raw : REAL;

    (* Processed outputs *)
    pressure_psi : REAL;
    temp_f : REAL;
    temp_c : REAL;
    filtered_pressure : REAL;
    alarm_active : BOOL;

    (* Statistics *)
    pressure_avg : REAL;
    pressure_sd : REAL;
    samples : STRING;                  (* ARRAY handle *)
    sample_count : INT := 0;
END_VAR

(* Scale ADC to engineering units *)
pressure_psi := SCALE(INT_TO_REAL(adc_raw), 0.0, 4095.0, 0.0, 100.0);

(* Temperature conversion *)
temp_c := 25.0;
temp_f := C_TO_F(temp_c);

(* Exponential moving average filter *)
filtered_pressure := EMA('press_filter', pressure_psi, 0.15);

(* Hysteresis on alarm — prevents chatter near threshold *)
alarm_active := HYSTERESIS(filtered_pressure, 85.0, 90.0, alarm_active);

(* Clamp output to valid range *)
pressure_psi := CLAMP(pressure_psi, 0.0, 100.0);

(* Collect samples for statistics *)
sample_count := sample_count + 1;
IF sample_count = 1 THEN
    samples := ARRAY_CREATE(filtered_pressure);
ELSE
    samples := ARRAY_APPEND(samples, filtered_pressure);
    IF ARRAY_LENGTH(samples) > 100 THEN
        samples := ARRAY_SLICE(samples, 1, 100);    (* Keep last 100 *)
    END_IF;
END_IF;

IF ARRAY_LENGTH(samples) >= 10 THEN
    pressure_avg := MEAN(samples);
    pressure_sd := STDDEV(samples);
END_IF;

(* Format for display *)
display_text := FORMAT('Pressure: %.1f PSI (avg: %.1f, sd: %.2f)',
                       filtered_pressure, pressure_avg, pressure_sd);

END_PROGRAM

GoPLC v1.0.535 | Math, String & Type Conversion Reference | IEC 61131-3 + Extensions