From 343f484c382fd1e074db7969bbca4ee01370378f Mon Sep 17 00:00:00 2001
From: Marcel Keller <mks.keller@gmail.com>
Date: Fri, 4 Jan 2019 17:33:12 +0100
Subject: [PATCH] Variable precision for floating-point outputs.

---
 Compiler/instructions.py      | 5 +++++
 Compiler/instructions_base.py | 1 +
 Compiler/library.py           | 3 +++
 GC/Processor.h                | 1 +
 GC/Processor.hpp              | 7 +++++++
 GC/instructions.h             | 1 +
 Processor/Instruction.cpp     | 5 +++++
 Processor/Instruction.h       | 1 +
 Programs/Source/tutorial.mpc  | 4 ++++
 9 files changed, 28 insertions(+)

diff --git a/Compiler/instructions.py b/Compiler/instructions.py
index 04bd560c..18a07121 100644
--- a/Compiler/instructions.py
+++ b/Compiler/instructions.py
@@ -952,6 +952,11 @@ class print_float_plain(base.IOInstruction):
     code = base.opcodes['PRINTFLOATPLAIN']
     arg_format = ['c', 'c', 'c', 'c']
 
+class print_float_prec(base.IOInstruction):
+    __slots__ = []
+    code = base.opcodes['PRINTFLOATPREC']
+    arg_format = ['int']
+
 class print_char(base.IOInstruction):
     r""" Print a single character to stdout. """
     code = base.opcodes['PRINTCHR']
diff --git a/Compiler/instructions_base.py b/Compiler/instructions_base.py
index 382fbd5c..dde5c3a6 100644
--- a/Compiler/instructions_base.py
+++ b/Compiler/instructions_base.py
@@ -163,6 +163,7 @@ opcodes = dict(
     WRITEFILESHARE = 0xBD,     
     READFILESHARE = 0xBE,
     CONDPRINTSTR = 0xBF,
+    PRINTFLOATPREC = 0xE0,
     GBITDEC = 0x184,
     GBITCOM = 0x185,
     # Secure socket
diff --git a/Compiler/library.py b/Compiler/library.py
index d56c9a73..01577bb5 100644
--- a/Compiler/library.py
+++ b/Compiler/library.py
@@ -103,6 +103,9 @@ def print_ln_if(cond, s):
             cond.print_if(s[:4])
             s = s[4:]
 
+def print_float_precision(n):
+    print_float_prec(n)
+
 def runtime_error(msg='', *args):
     """ Print an error message and abort the runtime. """
     print_str('User exception: ')
diff --git a/GC/Processor.h b/GC/Processor.h
index a05f8682..76d5b234 100644
--- a/GC/Processor.h
+++ b/GC/Processor.h
@@ -87,6 +87,7 @@ public:
     void print_chr(int n);
     void print_str(int n);
     void print_float(const vector<int>& args);
+    void print_float_prec(int n);
 };
 
 template <class T>
diff --git a/GC/Processor.hpp b/GC/Processor.hpp
index 60ba2cb9..20769f08 100644
--- a/GC/Processor.hpp
+++ b/GC/Processor.hpp
@@ -6,6 +6,7 @@
 #include <GC/Processor.h>
 
 #include <iostream>
+#include <iomanip>
 using namespace std;
 
 #include "GC/Program.h"
@@ -224,4 +225,10 @@ void Processor<T>::print_float(const vector<int>& args)
     T::out << bigint::get_float(C[args[0]], C[args[1]], C[args[2]], C[args[3]]) << flush;
 }
 
+template <class T>
+void Processor<T>::print_float_prec(int n)
+{
+    T::out << setprecision(n);
+}
+
 } /* namespace GC */
diff --git a/GC/instructions.h b/GC/instructions.h
index b8551e0f..36284dee 100644
--- a/GC/instructions.h
+++ b/GC/instructions.h
@@ -78,6 +78,7 @@
     X(PRINTCHR, PROC.print_chr(IMM)) \
     X(PRINTSTR, PROC.print_str(IMM)) \
     X(PRINTFLOATPLAIN, PROC.print_float(EXTRA)) \
+    X(PRINTFLOATPREC, PROC.print_float_prec(IMM)) \
     X(CONDPRINTSTR, if(C0.get()) PROC.print_str(IMM)) \
     X(LDINT, I0 = int(IMM)) \
     X(ADDINT, I0 = I1 + I2) \
diff --git a/Processor/Instruction.cpp b/Processor/Instruction.cpp
index aa1f4469..ea0d1a6d 100644
--- a/Processor/Instruction.cpp
+++ b/Processor/Instruction.cpp
@@ -18,6 +18,7 @@
 #include <algorithm>
 #include <sstream>
 #include <map>
+#include <iomanip>
 
 #include "Tools/callgrind.h"
 
@@ -261,6 +262,7 @@ void BaseInstruction::parse_operands(istream& s, int pos)
       case START:
       case STOP:
       case LISTEN:
+      case PRINTFLOATPREC:
         n = get_int(s);
         break;
       // instructions with no operand
@@ -1503,6 +1505,9 @@ inline void Instruction::execute(Processor<sint, sgf2n>& Proc) const
             Proc.out << bigint::get_float(v, exp, z, s) << flush;
           }
       break;
+      case PRINTFLOATPREC:
+        Proc.out << setprecision(n);
+        break;
       case PRINTSTR:
            {
              Proc.out << string((char*)&n,sizeof(n)) << flush;
diff --git a/Processor/Instruction.h b/Processor/Instruction.h
index 96c68c65..01144782 100644
--- a/Processor/Instruction.h
+++ b/Processor/Instruction.h
@@ -166,6 +166,7 @@ enum
     WRITEFILESHARE = 0xBD,
     READFILESHARE = 0xBE,
     CONDPRINTSTR = 0xBF,
+    PRINTFLOATPREC = 0xE0,
 
     // GF(2^n) versions
     
diff --git a/Programs/Source/tutorial.mpc b/Programs/Source/tutorial.mpc
index 7567e605..b9c84e67 100644
--- a/Programs/Source/tutorial.mpc
+++ b/Programs/Source/tutorial.mpc
@@ -57,6 +57,10 @@ test(a[99], 99 * 98)
 
 sfix.set_precision(16, 32)
 
+# and the output precision in decimal digits
+
+print_float_precision(4)
+
 # you can do all basic arithmetic with sfix, including division
 
 a = sfix(2)