math: add simple fib function (#22)

src/lang/bool.sh

@@ -137,6 +137,20 @@ function is_int() {
         [ "${val}" = "${res}" ]
 }
 
+function is_uint() {
+        # True if the given value is an unsigned int (bc).
+        local ctx; is_ctx "${1}" && ctx="${1}" && shift
+        [ $# -ne 1 ] && { ctx_wn $ctx; return $EC; }
+        local -r val="${1}"
+        shift 1 || { ctx_wn $ctx; return $EC; }
+
+        ! is_int "${val}" && return $FALSE
+
+        [[ "${val:0:1}" == "-" ]] && return $FALSE
+
+        return $TRUE
+}
+
 function is_float() {
         # True if the given value can be a float (bc).
         local ctx; is_ctx "${1}" && ctx="${1}" && shift

src/lang/bool_test.sh

@@ -179,6 +179,23 @@ function test_is_int() {
 }
 readonly -f test_is_int
 
+function test_is_uint() {
+        is_uint 10 || \
+                return $EC
+
+        is_uint abc && \
+                return $EC
+
+        is_uint 10.2 && \
+                return $EC
+
+        is_uint -10 && \
+                return $EC
+
+        return 0
+}
+readonly -f test_is_uint
+
 function test_is_float() {
         is_float 1.2 || \
                 return $EC

src/util/math.sh

@@ -289,3 +289,26 @@ function math_ceil() {
         res=$(bc -l <<< "scale=0; ( ${val} + 1 ) / 1")
         echo "${res}"
 }
+
+function math_fib() {
+        # Return fibonacci for the given `n`.
+        local ctx; is_ctx "${1}" && ctx="${1}" && shift
+        [ $# -ne 1 ] && { ctx_wn $ctx; return $EC; }
+        local n="${1}"
+        shift 1 || { ctx_wn $ctx; return $EC; }
+
+        [ -z "${n}" ] && { ctx_w $ctx "no n"; return $EC; }
+        ! is_uint "${n}" && { ctx_w $ctx "not an int"; return $EC; }
+
+        local f0=0
+        local f1=1
+
+        local res=0
+        for (( i=1; i<${n}; i++ )); do
+                res=$(( ${f0} + ${f1} ))
+                f0=${f1}
+                f1=${res}
+        done
+
+        echo "${res}"
+}

src/util/math_test.sh

@@ -222,3 +222,24 @@ function test_math_ceil() {
         assert_eq 0 $(math_ceil "-0.8")
 }
 readonly -f test_math_ceil
+
+function test_math_fib() {
+        local res
+
+        res=$(math_fib 13)
+        [ "${res}" -ne 233 ] && \
+                assert_fail "13 incorrect"
+
+        res=$(math_fib 23)
+        [ "${res}" -ne 28657 ] && \
+                assert_fail "23 incorrect"
+
+        math_fib -10 && \
+                assert_fail "negative is not allowed"
+
+        math_fib "abc" && \
+                assert_fail "has to fail with non int"
+
+        return 0
+}
+readonly -f test_math_fib