Type conversion

logiccloud does not hand-write one conversion function per type pair. Instead it generates a conversion function for every valid combination of source and target type, following a small set of naming rules. Rather than listing the hundreds of resulting names, this page documents the rules and the type set they range over — once you know the rule, you know the function name.

Every conversion function takes a single input parameter named IN of the source type and returns the target type.

r := INT_TO_REAL(counter);
b := REAL_TO_BYTE(level);

General conversion — <FROM>_TO_<TO>

The general rule produces a function for every ordered pair of distinct types drawn from the conversion type set below:

<FROM>_TO_<TO>(IN : <FROM>) : <TO>

Examples: INT_TO_REAL, REAL_TO_DINT, WORD_TO_INT, BOOL_TO_BYTE, STRING_TO_INT, TIME_TO_LTIME, DATE_TO_DT.

Source / target type set

The same set is used for both the <FROM> and <TO> side (a type is never converted to itself):

Group	Types
Boolean	BOOL
Bit string	BYTE, WORD, DWORD, LWORD
Signed integer	SINT, INT, DINT, LINT
Unsigned integer	USINT, UINT, UDINT, ULINT
Real	REAL, LREAL
Character	CHAR, WCHAR
String	STRING, WSTRING
Duration	TIME, LTIME
Date	DATE, LDATE
Time of day	TOD, LTOD
Date and time	DT, LDT

Note

A conversion exists for every distinct ordered pair from this set — that is the rule. Whether a particular conversion is meaningful for your data is up to you; e.g. STRING_TO_INT parses, DT_TO_DATE narrows. The transpiler validates the argument type against the <FROM> part of the name.

Real truncation — <REAL>_TRUNC_<TO>

In addition to the rounding behavior of the general rule, the real types get a dedicated truncating conversion to every target type. Truncation discards the fractional part rather than rounding it.

REAL_TRUNC_<TO>(IN : REAL) : <TO>
LREAL_TRUNC_<TO>(IN : LREAL) : <TO>

The <TO> side ranges over the full conversion type set above. Examples: REAL_TRUNC_INT, REAL_TRUNC_DINT, LREAL_TRUNC_LINT.

whole := REAL_TRUNC_INT(3.9);   // 3, not 4

BCD conversion — _BCD_TO_ and _TO_BCD_

BCD (binary-coded decimal) conversions are generated only between the integer, bit-string and string groups — i.e. <FROM> and <TO> are each one of:

• Signed integers: SINT, INT, DINT, LINT
• Unsigned integers: USINT, UINT, UDINT, ULINT
• Bit strings: BYTE, WORD, DWORD, LWORD
• Strings: STRING, WSTRING

Two directions are generated for each ordered pair:

<FROM>_BCD_TO_<TO>(IN : <FROM>) : <TO>   // interpret IN as BCD, produce binary <TO>
<FROM>_TO_BCD_<TO>(IN : <FROM>) : <TO>   // encode IN as BCD into <TO>

Examples: BYTE_BCD_TO_INT, INT_TO_BCD_WORD, WORD_BCD_TO_USINT.

value := BYTE_BCD_TO_INT(thumbwheel);   // decode a BCD thumbwheel
display := INT_TO_BCD_WORD(value);      // re-encode for a BCD display

Caution

BCD conversions are not generated for REAL/LREAL, character, duration, date or time-of-day types — only the integer, bit-string and string groups listed above. Use the general <FROM>_TO_<TO> rule for the other types.

Use IS_VALID_BCD to check that a bit string holds a valid BCD value before decoding it.