hex.sub.sub_constant_with_leading_zeros

Internal helper for hex.sub_constant: strips const’s trailing zero nibbles, then subtracts the result from dst[:n] at the matching nibble offset (so the trailing zeros are skipped instead of materialised as wasted-work subtractions).

n_const is the minimal hex.vec size needed to store const.

Signature

def sub_constant_with_leading_zeros n, dst, const, leading_lsb_const_zeros { ... }

Defined in hex/math.fj — lines 193–195 (view on GitHub).

Complexity

• Time: n_const(4@+12) + 5@+2

• Space: n_const(2.5@+39) + (dst_n - hex_shift)(1.5@+13) + 4@+29

See the complexity glossary for what @, w, dw, dbit, n mean.

Source

Click to view the macro body

def sub_constant_with_leading_zeros n, dst, const, leading_lsb_const_zeros {
    .sub_hex_shifted_constant n, dst, const >> (leading_lsb_const_zeros & (0-4)), leading_lsb_const_zeros >> 2
}

Depends on

• hex.sub.sub_hex_shifted_constant/4

Used by

• hex.sub_constant

Example uses

• hex.sub_constant in hex/math.fj

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