diff --git a/_02_.Writing-programs.sz b/_02_.Writing-programs.sz index 9677a5d..ffb9fff 100644 --- a/_02_.Writing-programs.sz +++ b/_02_.Writing-programs.sz @@ -627,7 +627,6 @@ So one thing needs no brackets, and several things are a vec: @codeblock[#:lang "bjolang"]|{ (def name "Ada") -(: n int) (def n 3) (show "Hello\n") ;; Hello @@ -658,7 +657,7 @@ Anything else is converted first: @code{BStr}, @code{BInt}, @code{BChar} and @code{BMany} are the cases of @code{Block}. You rarely write them, but like any constructor they are functions, so @code{(vec-map BStr names)} is a vec of blocks. -@strong{A number bound by @code{def}.} The @code{(: n int)} above is needed. @code{(def n 3)} alone does not say which kind of number @code{n} is, as it could still become a long or a double, so it cannot be read as a block, and the compiler says so at @code{n}. The same holds for @code{(def xs [1 2 3])} and @code{(def total (+ 1 2))}. A number that comes from a typed parameter, a record field or a function such as @code{vec-length} has its type already, and a number written in the vec itself, as in @code{["n = " 3]}, is an int. +@strong{A number bound by @code{def}.} @code{(def n 3)} does not say which kind of number @code{n} is: it could still become a long or a double. Where a block is wanted, it is read as the number written there would be, so @code{["n = " n]} is what @code{["n = " 3]} is, and @code{n} is an int from then on. A number that is used as a double later, as in @code{(+ n 0.5)}, needs @code{(: n double)} above its @code{def}. @strong{Where a block is wanted.} A string or a vec is read as a block where the compiler knows that a block is wanted: as an argument, as what a function declared to return a @code{Block} returns, and as the value of a binding whose type is written, such as @code{(: parts Block)}. A @code{def} without a type is what its value is: @code{(def parts ["a" "b"])} is a @code{(Vec string)}, and @code{(show parts)} is refused. Write @code{(: parts Block)} above it. @@ -928,7 +927,6 @@ The messages for the common mistakes, and what to write instead: | Block: ... found the number 1.5 | @code{(numeric 1.5)} | | Block: ... found a boolean, or found a bool | @code{(if b "yes" "no")} | | Block: ... found a (Vec string) | @code{(vec-map BStr xs)}, or @code{(: xs Block)} above @code{(def xs ...)} | -| Block: 'n' is a number, and nothing says yet whether it is an int ... | @code{(: n int)} above @code{(def n 3)} | | Block: ... found a (Vec (Vec ...)), at a lambda that returns a vec | @code{(each [...])} around the vec the lambda returns | }