IDC: Expressions

IDC: Expressions

In the IDC expressions you can use almost all C operations except:

  complex assigment operations as '+='
  , (comma operation)
  [] (array indexing, there are no arrays in IDC)

You can use the following construct in the expressions:

  [ s, o ]

(This means to calculate linear (effective) address for segment 's' offset 'o'.) The calculation is made using the following formula:

  (s << 4) + o

If a string constant is specified as 's', it denotes a segment by its name.

There are 3 type conversion operations:

  long(expr)  floating point numbers are truncated during conversion
  char(expr)
  float(expr)

However, there is no need in explicit type conversions because all type conversions are made automatically:

  - addition:
        if both operands are strings,
          string addition is performed (strings are concatenated);
        if floating point operand exists,
          both operands are converted to floats;
        otherwise
          both operands are converted to longs;

  - subtraction/multiplication/division:
        if floating point operand exists,
          both operands are converted to floats;
        otherwise
          both operands are converted to longs;

  - comparisions (==,!=, etc):
        if both operands are strings, string comparison is performed;
        if floating point operand exists,
          both operands are converted to floats;
        otherwise
          both operands are converted to longs;

  - all other operations:
        operand(s) are converted to longs;

There is one notable exception concerning type conversions: if one operand is a string and the other is zero (0), then a string operation is performed. Zero is converted to an empty string in this case. Index | Previous topic | Next topic