X-Git-Url: https://jxself.org/git/?p=ibg.git;a=blobdiff_plain;f=chapters%2F14.rst;h=e9f2a8da31c935556c1c0f437a4d52076713a1fc;hp=9a62a74e1ab558f410683e79b752900521d884c5;hb=8009937904cf79341a9c23c9c5e7b541606bfcb6;hpb=fb8b7c14f10733e913e2b87f9a82e5b44c0dc7be diff --git a/chapters/14.rst b/chapters/14.rst index 9a62a74..e9f2a8d 100644 --- a/chapters/14.rst +++ b/chapters/14.rst @@ -85,93 +85,89 @@ player), and we use the placeholders `{obj_id}`, `{var_id}`, Statements ========== -.. todo:: - - We might need some custom syntax highlighting here. - A :term:`statement` is an instruction intended for the interpreter, telling it what to do at run-time. It *must* be given in lower-case, and always ends with a semicolon. Some statements, like ``if``, control one or more other statements. We use the placeholder `{statement_block}` to represent either a single -`{statement}`, or any number of `{statements}` enclosed in braces:: +`{statement}`, or any number of `{statements}` enclosed in braces: - statement; - - { statement; statement; ... statement; } + | `{statement};` + | + | `{statement}; {statement}; ... {statement};` Statements that we've met ------------------------- Our games have used these statements, about half of the Inform -possibilities:: - - give obj_id attribute; - give obj_id attribute attribute ... attribute; - - if (expression) statement_block - if (expression) statement_block else statement_block - - move obj_id to parent_obj_id; - - objectloop (var_id) statement_block - - print value; - print value, value, ... value; - - print_ret value; - print_ret value, value, ... value; - - remove obj_id; - - return false; - return true; - - style underline; print...; style roman; - - switch (expression) { - value: statement; statement; ... statement; - ... - default: statement; statement; ... statement; - } - - "string"; - "string", value, ... value; - - ; - ; - ; - - <>; - <>; - <>; +possibilities: + + | `give {obj_id} {attribute};` + | `give {obj_id} {attribute} {attribute} ... {attribute};` + | + | `if ({expression}) {statement_block}` + | `if ({expression}) {statement_block} else {statement_block}` + | + | `move {obj_id} to {parent_obj_id};` + | + | `objectloop ({var_id}) {statement_block}` + | + | `print {value};` + | `print {value}, {value}, ... {value};` + | + | `print_ret {value};` + | `print_ret {value}, {value}, ... {value};` + | + | `remove {obj_id};` + | + | `return false;` + | `return true;` + | + | `style underline; print...; style roman;` + | + | `switch ({expression}) {` + | `{value}: {statement}; {statement}; ... {statement};` + | `...` + | `default: {statement}; {statement}; ... {statement};` + | `}` + | + | `"{string}";` + | `"{string}", {value}, ... {value};` + | + | `<{action}>;` + | `<{action} {noun}>;` + | `<{action} {noun} {second}>;` + | + | `<<{action}>>;` + | `<<{action} {noun}>>;` + | `<<{action} {noun} {second}>>;` Statements that we've not met ----------------------------- Although our example games haven't needed to use them, these looping -statements are sometimes useful:: - - break; - continue; +statements are sometimes useful: - do statement_block until (expression) - - for (set_var : loop_while_expression : update_var) statement_block - - while (expression) statement_block + | `break;` + | `continue;` + | + | `do {statement_block} until ({expression})` + | + | `for ({set_var} : {loop_while_expression} : {update_var}) {statement_block}` + | + | `while ({expression}) {statement_block}` On the other hand, we suggest that you put the following statements on hold for now; they're not immediately relevant to everyday code and have -mostly to do with printing and formatting:: +mostly to do with printing and formatting: - box - font - jump - new_line - spaces - string + | `box` + | `font` + | `jump` + | `new_line` + | `spaces` + | `string` In particular, avoid using the deprecated jump statement if you possibly can. @@ -306,6 +302,11 @@ two-state variables are attributes. Properties ---------- +.. Generated by autoindex +.. index:: + pair: before; library property + pair: name; library property + The library defines around forty-eight standard property variables (such as :prop:`before` or :prop:`name`), but you can readily create further ones just by using them within an object definition. @@ -408,6 +409,10 @@ or implicitly when the routine runs out of statements. If none of these [ routine_id; statement; statement; ... statement; ]; +.. Generated by autoindex +.. index:: + pair: true; library constant + returns :const:`true` and :: property [; statement; statement; ... statement; ] @@ -663,6 +668,11 @@ you'll come across. "number" property and "general" attribute ----------------------------------------- +.. Generated by autoindex +.. index:: + pair: general; library attribute + pair: number; library property + The library defines a standard :prop:`number` property and a standard :attr:`general` attribute, whose roles are undefined: they are general-purpose variables available within every object to designers as @@ -705,6 +715,10 @@ is virtually unlimited. Setting up the object tree -------------------------- +.. Generated by autoindex +.. index:: + pair: found_in; library property + Throughout this guide, we've defined the initial position of each object within the overall object tree either by explicitly mentioning its parent's ``obj_id`` (if any) in the first line of the object definition