custodi

Groups early-exit guard checks before the main body of a function.

Aliases: guard

Syntax: custodi <block>

Category

control-flow

Related

• si
• ergo
• redde

Examples

examples/corpus/custodi/custodi.fab (canonical · keyword)

Groups early-exit guard checks before the main body of a function.

# custodi — guard blocks for early exit
#
# custodi { si <conditio> { <exitus> } }
#
# GRAMMAR:
#   custodiStmt :← 'custodi' '{' stmt* '}'
#
# EXPECTED OUTPUT:
#   Division, clamping, and range-validation scalar results.

functio divide(numerus a, numerus b) → numerus {
    custodi {
        si b ≡ 0 {
            redde 0
        }
    }

    redde a / b
}

functio tracta(numerus x) → numerus {
    custodi {
        si x < 0 {
            redde -1
        }
        si x > 100 {
            redde -1
        }
    }

    # Main logic, clearly separated from custodi
    redde x * 2
}

functio stringe(numerus valor, numerus minimum, numerus maximum) → numerus {
    custodi {
        si minimum > valor {
            redde minimum
        }
        si maximum < valor {
            redde maximum
        }
    }

    redde valor
}

incipit {
    # Guard returns 0 instead of dividing by zero
    nota divide(10, 2)
    nota divide(10, 0)

    # Out-of-range inputs short-circuit to -1
    nota tracta(50)
    nota tracta(-10)
    nota tracta(150)

    nota stringe(5, 0, 10)
    nota stringe(-5, 0, 10)
    nota stringe(15, 0, 10)
}

Expected output:

5
0
100
-1
-1
5
0
10