Types
Value Types
Value types are encoded by a single byte.
\[\begin{split}\begin{array}{llclll@{\qquad\qquad}l}
\def\mathdef902#1{{}}\mathdef902{value type} & \href{../binary/types.html#binary-valtype}{\mathtt{valtype}} &::=&
\def\mathdef939#1{\mathtt{0x#1}}\mathdef939{7F} &\Rightarrow& \href{../syntax/types.html#syntax-valtype}{\mathsf{i32}} \\ &&|&
\def\mathdef940#1{\mathtt{0x#1}}\mathdef940{7E} &\Rightarrow& \href{../syntax/types.html#syntax-valtype}{\mathsf{i64}} \\ &&|&
\def\mathdef941#1{\mathtt{0x#1}}\mathdef941{7D} &\Rightarrow& \href{../syntax/types.html#syntax-valtype}{\mathsf{f32}} \\ &&|&
\def\mathdef942#1{\mathtt{0x#1}}\mathdef942{7C} &\Rightarrow& \href{../syntax/types.html#syntax-valtype}{\mathsf{f64}} \\
\end{array}\end{split}\]
Note
Value types can occur in contexts where type indices are also allowed, such as in the case of block types.
Thus, the binary format for types corresponds to the signed LEB128 encoding of small negative \(\href{../syntax/values.html#syntax-int}{\mathit{s}N}\) values, so that they can coexist with (positive) type indices in the future.
Result Types
Result types are encoded by the respective vectors of value types `.
\[\begin{split}\begin{array}{llclll@{\qquad\qquad}l}
\def\mathdef902#1{{}}\mathdef902{result type} & \href{../binary/types.html#binary-resulttype}{\mathtt{resulttype}} &::=&
t^\ast{:\,}\href{../binary/conventions.html#binary-vec}{\mathtt{vec}}(\href{../binary/types.html#binary-valtype}{\mathtt{valtype}}) &\Rightarrow& [t^\ast] \\
\end{array}\end{split}\]
Function Types
Function types are encoded by the byte \(\def\mathdef943#1{\mathtt{0x#1}}\mathdef943{60}\) followed by the respective vectors of parameter and result types.
\[\begin{split}\begin{array}{llclll@{\qquad\qquad}l}
\def\mathdef902#1{{}}\mathdef902{function type} & \href{../binary/types.html#binary-functype}{\mathtt{functype}} &::=&
\def\mathdef944#1{\mathtt{0x#1}}\mathdef944{60}~~\mathit{rt}_1{:\,}\href{../binary/types.html#binary-resulttype}{\mathtt{resulttype}}~~\mathit{rt}_2{:\,}\href{../binary/types.html#binary-resulttype}{\mathtt{resulttype}}
&\Rightarrow& \mathit{rt}_1 \href{../syntax/types.html#syntax-functype}{\rightarrow} \mathit{rt}_2 \\
\end{array}\end{split}\]
Limits
Limits are encoded with a preceding flag indicating whether a maximum is present.
\[\begin{split}\begin{array}{llclll}
\def\mathdef902#1{{}}\mathdef902{limits} & \href{../binary/types.html#binary-limits}{\mathtt{limits}} &::=&
\def\mathdef945#1{\mathtt{0x#1}}\mathdef945{00}~~n{:}\href{../binary/values.html#binary-int}{\def\mathdef907#1{{\mathtt{u}#1}}\mathdef907{\mathtt{32}}} &\Rightarrow& \{ \href{../syntax/types.html#syntax-limits}{\mathsf{min}}~n, \href{../syntax/types.html#syntax-limits}{\mathsf{max}}~\epsilon \} \\ &&|&
\def\mathdef946#1{\mathtt{0x#1}}\mathdef946{01}~~n{:}\href{../binary/values.html#binary-int}{\def\mathdef907#1{{\mathtt{u}#1}}\mathdef907{\mathtt{32}}}~~m{:}\href{../binary/values.html#binary-int}{\def\mathdef907#1{{\mathtt{u}#1}}\mathdef907{\mathtt{32}}} &\Rightarrow& \{ \href{../syntax/types.html#syntax-limits}{\mathsf{min}}~n, \href{../syntax/types.html#syntax-limits}{\mathsf{max}}~m \} \\
\end{array}\end{split}\]
Memory Types
Memory types are encoded with their limits.
\[\begin{split}\begin{array}{llclll@{\qquad\qquad}l}
\def\mathdef902#1{{}}\mathdef902{memory type} & \href{../binary/types.html#binary-memtype}{\mathtt{memtype}} &::=&
\mathit{lim}{:}\href{../binary/types.html#binary-limits}{\mathtt{limits}} &\Rightarrow& \mathit{lim} \\
\end{array}\end{split}\]
Table Types
Table types are encoded with their limits and a constant byte indicating their element type.
\[\begin{split}\begin{array}{llclll}
\def\mathdef902#1{{}}\mathdef902{table type} & \href{../binary/types.html#binary-tabletype}{\mathtt{tabletype}} &::=&
\mathit{et}{:}\href{../binary/types.html#binary-elemtype}{\mathtt{elemtype}}~~\mathit{lim}{:}\href{../binary/types.html#binary-limits}{\mathtt{limits}} &\Rightarrow& \mathit{lim}~\mathit{et} \\
\def\mathdef902#1{{}}\mathdef902{element type} & \href{../binary/types.html#binary-elemtype}{\mathtt{elemtype}} &::=&
\def\mathdef947#1{\mathtt{0x#1}}\mathdef947{70} &\Rightarrow& \href{../syntax/types.html#syntax-elemtype}{\mathsf{funcref}} \\
\end{array}\end{split}\]
Global Types
Global types are encoded by their value type and a flag for their mutability.
\[\begin{split}\begin{array}{llclll}
\def\mathdef902#1{{}}\mathdef902{global type} & \href{../binary/types.html#binary-globaltype}{\mathtt{globaltype}} &::=&
t{:}\href{../binary/types.html#binary-valtype}{\mathtt{valtype}}~~m{:}\href{../binary/types.html#binary-mut}{\mathtt{mut}} &\Rightarrow& m~t \\
\def\mathdef902#1{{}}\mathdef902{mutability} & \href{../binary/types.html#binary-mut}{\mathtt{mut}} &::=&
\def\mathdef948#1{\mathtt{0x#1}}\mathdef948{00} &\Rightarrow& \href{../syntax/types.html#syntax-mut}{\mathsf{const}} \\ &&|&
\def\mathdef949#1{\mathtt{0x#1}}\mathdef949{01} &\Rightarrow& \href{../syntax/types.html#syntax-mut}{\mathsf{var}} \\
\end{array}\end{split}\]