CBM floating-point support¶

The assembler evaluates CBM five-byte floating-point values using the BASIC/KERNAL ROM math routines.

Expressions and output¶

.eq HALF .5
.eq NEG -1.5
.eq THIRD FLOAT(1)/3

.df HALF, NEG, THIRD      ; three five-byte CBM floats
.dw INT(HALF*1000)        ; 500
.db ROUND(HALF*255)       ; 128

.if HALF                 ; zero is false; every nonzero float is true
    .db 1
.endif

.if HALF >= .5
    .db 2
.endif

Literals accept decimal fractions as well as scientific notation: 1.5, .5, 1e3, 1.5e-2. Unary + and - work on values and parenthesized expressions. Float arithmetic supports +, -, *, and /. Mixed integer/float operations promote the integer to a float and evaluate to a float result.

The .EQ directive preserves the result’s type. .DF, on the other hand, promotes its final result if necessary and always emits a 5-byte CBM float value.

Integer only operations otherwise always produce an integer result type.

Note

1/3 is zero, including in .DF 1/3. Use FLOAT(1)/3 or 1.0/3.
-1 wraps to 65535. Use -1.0 or -FLOAT(1) for a negative float.
^ remains bitwise XOR, not exponentiation.
. remains bitwise OR where it cannot be a decimal point. Write 3 . 14 for OR; 3.14 is a float. A trailing decimal point alone is not a float marker.

Byte/word output, addresses, counts, and bitwise operations all require a float to be integral and within the range [0, 65535]. Fractions and negative or out-of-range values generate an error.

Functions¶

Function names are case-insensitive to the assembler. They must be immediately followed by their opening parenthesis. If they are not, they will be treated as symbols (sin is a valid symbol name).

Functions may also be nested.

Function	Result
`ABS(x)`	Absolute value as a float
`CEIL(x)`	Integral float, rounded toward positive infinity
`COS(x)`	Cosine (x is in radians)
`EXP(x)`	Natural exponent
`FLOAT(x)`	Promotes an unsigned integer or preserves a float
`FLOOR(x)`	Integral float, rounded toward negative infinity
`LOG(x)`	Natural logarithm
`INT(x)`	Unsigned integer, only if x is exactly integral and in 0..65535
`SIN(x)`	Sine (x is in radians)
`SQRT(x)`	Square root
`ROUND(x)`	Integral float, nearest integer; halfway cases away from zero
`TRUNC(x)`	Integral float, rounded toward zero

NOTE: INT is a custom conversion, not Commodore BASIC’s flooring INT function; use FLOOR for that behavior.

In general, do not depend on floats cleanly producing an integer value. For example, use ROUND(SQRT(9.0)); do not depend on an approximate result being exactly integral.